Fin-like field effect transistor patterning methods for increasing process margins

ABSTRACT

Methods are disclosed herein for patterning integrated circuit devices, such as fin-like field effect transistor devices. An exemplary method includes forming a material layer that includes an array of fin features, and performing a fin cut process to remove a subset of the fin features. The fin cut process includes exposing the subset of fin features using a cut pattern and removing the exposed subset of the fin features. The cut pattern partially exposes at least one fin feature of the subset of fin features. In implementations where the fin cut process is a fin cut first process, the material layer is a mandrel layer and the fin features are mandrels. In implementations where the fin cut process is a fin cut last process, the material layer is a substrate (or material layer thereof), and the fin features are fins defined in the substrate (or material layer thereof).

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs, where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component (or line) that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs.

Such scaling down has also increased the complexity of processing andmanufacturing ICs and, for these advances to be realized, similardevelopments in IC processing and manufacturing are needed. For example,as fin-like field effect transistor (FinFET) technologies progresstowards smaller feature sizes (such as 32 nanometers, 28 nanometers, 20nanometers, and below), FinFET patterning processes are significantlyconstrained by decreasing process margins, including decreasing overlaymargins. Accordingly, although existing fin patterning processes havebeen generally adequate for their intended purposes, they have not beenentirely satisfactory in all respects

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 is a flow chart of a method for fabricating a semiconductordevice according to various aspects of the present disclosure.

FIGS. 2A-2I are fragmentary diagrammatic views of a FinFET device, inportion or entirety, at various fabrication stages, such as thoseassociated with the method of FIG. 1, according to various aspects ofthe present disclosure.

FIGS. 3A-3D are fragmentary top views of a FinFET device, in portion orentirety, at various stages of a fin cut process, according to variousaspects of the present disclosure.

FIGS. 4A-4I are fragmentary diagrammatic views of another FinFET device,in portion or entirety, at various fabrication stages, such as thoseassociated with the method of FIG. 1, according to various aspects ofthe present disclosure.

FIGS. 5A-5F are fragmentary diagrammatic views of yet another FinFETdevice, in portion or entirety, at various fabrication stages, such asthose associated with the method of FIG. 1, according to various aspectsof the present disclosure.

FIG. 6A and FIG. 6B are various views of a FinFET device, in portion orentirety, at stages of a fin cut process, according to various aspectsof the present disclosure.

FIGS. 7A-7F are fragmentary diagrammatic views of yet another FinFETdevice, in portion or entirety, at various fabrication stages, such asthose associated with the method of FIG. 1, according to various aspectsof the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact.

In addition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.Moreover, the formation of a feature on, connected to, and/or coupled toanother feature in the present disclosure that follows may includeembodiments in which the features are formed in direct contact, and mayalso include embodiments in which additional features may be formedinterposing the features, such that the features may not be in directcontact. In addition, spatially relative terms, for example, “lower,”“upper,” “horizontal,” “vertical,” “above,” “over,” “below,” “beneath,”“up,” “down,” “top,” “bottom,” etc. as well as derivatives thereof(e.g., “horizontally,” “downwardly,” “upwardly,” etc.) are used for easeof the present disclosure of one features relationship to anotherfeature. The spatially relative terms are intended to cover differentorientations of the device including the features.

FIG. 1 is a flow chart of a method 100 for fabricating an integratedcircuit (IC) device according to various aspects of the presentdisclosure. In some implementations, the IC device includes a fin-likefield effect transistor (FinFET) device, which generally refers to anyfin-based transistor device, such as a fin-based, multi-gate transistor.As described further below, method 100 can increase patterning processwindows, such as overlay process windows, ease IC manufacturability,and/or increase IC design layout flexibility. Additional steps can beprovided before, during, and after method 100, and some of the stepsdescribed can be moved, replaced, or eliminated for additionalembodiments of method 100.

At block 110, a material layer is formed that includes an array of finfeatures. In some implementations, the material layer is a mandrel layer(for example, including an array of mandrels) and the fin features aremandrels. In some implementations, the material layer is a fin layer ofa substrate (for example, including an array of fins) and the finfeatures are fins. The method proceeds to block 120 and block 130, wherea fin cut process is performed on the material layer to remove a subsetof the fin features. At block 120, the fin cut process includes exposingthe subset of fin features using a cut pattern, where the cut patternpartially exposes at least one fin feature of the subset of finfeatures. For example, a guarding material layer that includes a cutpattern is formed over the material layer, such that the guardingmaterial layer includes an opening that exposes the subset of the finfeatures. The opening partially exposes at least one fin feature, suchthat a portion (for example, a sidewall) of the at least one fin featureis free of the guarding material layer and a portion (for example,another sidewall) of the at least one fin feature is covered by theguarding material layer. At block 130, the fin cut process includesremoving the exposed subset of fin features, for example, by an etchingprocess. In implementations where the material layer is a mandrel layer,the fin cut process is a fin cut first process. In implementations wherethe material layer is a fin layer, the fin cut process is a fin cut lastprocess. At block 140, method 100 may continue to complete fabricationof the integrated circuit device. For example, in fin cut firstimplementations, method 100 can proceed with using the mandrel layer topattern an underlying layer to form one or more fins (in other words, afin layer) of a FinFET device. In some implementations, the underlyinglayer is a material layer of a substrate. In fin cut firstimplementations and fin cut last implementations, method 100 can proceedwith forming isolation features, such as shallow trench isolation (STI)features, in trenches defined by the fins of the fin layer.

Because method 100 partially exposes the subset of fin features to beremoved, instead of fully exposing the subset of fin features to beremoved, method 100 may be referred to as a partial open pattern etching(POPE) process. The discussion that follows illustrates FinFET devicesthat can be fabricated according to various embodiments of method 100.Though method 100 is applied herein to form fins of FinFET devices,method 100 can be applied in numerous ways to form other IC features ofIC devices. As one of many examples, POPE processes disclosed herein canbe implemented to form gate features and/or other IC features wherelarger patterning process windows are desired for easingmanufacturability and/or increasing IC design layout flexibility. SuchPOPE processes would involve exposing a subset of gate features (orother IC features) using a cut pattern, where the cut pattern partiallyexposes at least one gate feature (or other IC feature) of the subset ofgate features, and removing the exposed subset of gate features (orother IC features).

FIGS. 2A-2I are fragmentary diagrammatic views of a FinFET device 200,in portion or entirety, at various fabrication stages (such as thoseassociated with method 100) according to various aspects of the presentdisclosure. FinFET device 200 may be included in a microprocessor, amemory, and/or other integrated circuit device. In some implementations,FinFET device 200 may be a portion of an IC chip, a system on chip(SoC), or portion thereof, that includes various passive and activemicroelectronic devices such as resistors, capacitors, inductors,diodes, metal-oxide semiconductor field effect transistors (MOSFET),complementary metal-oxide semiconductor (CMOS) transistors, bipolarjunction transistors (BJTs), laterally diffused MOS (LDMOS) transistors,high voltage transistors, high frequency transistors, other suitablecomponents, or combinations thereof. FIGS. 2A-2I have been simplifiedfor the sake of clarity to better understand the inventive concepts ofthe present disclosure. Additional features can be added in FinFETdevice 200, and some of the features described below can be replaced,modified, or eliminated in other embodiments of FinFET device 200.

In FIG. 2A, FinFET device 200 includes a substrate (wafer) 210. In thedepicted embodiment, substrate 210 includes silicon. Alternatively oradditionally, substrate 210 includes another elementary semiconductor,such as germanium; a compound semiconductor, such as silicon carbide,gallium arsenide, gallium phosphide, indium phosphide, indium arsenide,and/or indium antimonide; an alloy semiconductor, such as silicongermanium (SiGe), GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP;or combinations thereof. Alternatively, substrate 210 is asemiconductor-on-insulator substrate, such as a silicon-on-insulator(SOI) substrate, a silicon germanium-on-insulator (SGOI) substrate, or agermanium-on-insulator (GOI) substrate. Semiconductor-on-insulatorsubstrates can be fabricated using separation by implantation of oxygen(SIMOX), wafer bonding, and/or other suitable methods.

Substrate 210 can include various doped regions (not shown) depending ondesign requirements of FinFET device 200. In some implementations,substrate 210 includes p-type doped regions (for example, p-type wells)doped with p-type dopants, such as boron (for example, BF₂), indium,other p-type dopant, or combinations thereof. In some implementations,substrate 210 includes n-type doped regions (for example, n-type wells)doped with n-type dopants, such as phosphorus, arsenic, other n-typedopant, or combinations thereof. In some implementations, substrate 210includes doped regions formed with a combination of p-type dopants andn-type dopants. The various doped regions can be formed directly onand/or in substrate 210, for example, providing a p-well structure, ann-well structure, a dual-well structure, a raised structure, orcombinations thereof. Doping may be implemented using a process such asion implantation or diffusion in various steps and techniques.

A patterning layer 220 is formed over substrate 210. In the depictedembodiment, patterning layer 220 is a tri-layer patterning stack, whichincludes a bottom patterning layer 222, a middle patterning layer 224,and an upper patterning layer 226. Suitable materials are selected forthese layers based, in part, on material etch selectivity. For example,bottom patterning layer 222, middle patterning layer 224, and upperpatterning layer 226 may be structured to have different materials, suchthat each layer can be removed using a corresponding etchant withoutsignificant etching of the other layers. In other words, bottompatterning layer 222, middle patterning layer 224, and upper patterninglayer 226 include materials having different etch rates. In someimplementations, upper patterning layer 226 can serve as an etch maskfor patterning middle patterning layer 224, bottom patterning layer 222,and/or substrate 210; middle patterning layer 224 can serve as an etchmask for patterning bottom patterning layer 222 and/or substrate 210;and bottom patterning layer 222 can serve as an etch mask for patterningsubstrate 210. In some implementations, bottom patterning layer 222,middle patterning layer 224, and upper patterning layer 226 includedifferent semiconductor materials and/or different dielectric materialsto achieve desired etching selectivity, such as silicon, amorphoussilicon, semiconductor oxide (for example, silicon oxide (SiO₂)),semiconductor nitride (for example, silicon nitride (SiN)),semiconductor oxynitride (for example, silicon oxynitride (SiON)),and/or semiconductor carbide (for example, silicon carbide (SiC)), othersemiconductor material, and/or other dielectric material. For example,in some implementations, bottom patterning layer 222 includes SiO₂,middle patterning layer 224 includes SiN, and upper patterning layer 226includes SiO₂. In some implementations, bottom patterning layer 222,middle patterning layer 224, and upper patterning layer 226 includedifferent resist materials to achieve desired etching selectivity. Insome implementations, bottom patterning layer 222 and upper patterninglayer 226 include organic materials, while middle patterning layer 226includes inorganic materials. Patterning layer 220 is formed by anysuitable process. For example, bottom patterning layer 222, middlepatterning layer 224, and upper patterning layer 226 can each be formedby a respective spin-coating process followed by a thermal bakingprocess. While patterning layer 220 is depicted as a tri-layerpatterning stack, patterning layer 220 can include any number of layersto achieve desired patterning results.

A mandrel layer 230 is formed over patterning layer 220. In the depictedembodiment, mandrel layer 230 includes an array of mandrels 232 (eachhaving a width w) disposed on upper patterning layer 226, where adjacentmandrels 232 are separated by a space S. Mandrels 232 have a pitch P,where pitch generally refers to a sum of a width of an IC feature (suchas w of mandrels 232) and a width of a space adjacent to the IC feature(such as S between mandrels 232) (in other words, P=w+S). Mandrels 232correspond with fin structures (alternatively referred to as fins) to beformed in an underlying layer of FinFET device 200, such that mandrels232 are also referred to as fin features. In some implementations, pitchP is a minimum pitch achievable between mandrels 232 by a lithographyprocess for a given technology node. Mandrel layer 230 includes amaterial that is different than patterning layer 220 (in particular,upper patterning layer 226) to achieve etching selectivity during anetching process, such that mandrel layer 230 can be removed using acorresponding etchant without significant etching of upper patterninglayer 226, and vice versa. In other words, mandrel layer 230 and upperpatterning layer 226 include materials having different etch rates. Insome implementations, mandrel layer 230 serves as an etching mask forpatterning layer 220. In some implementations, mandrel layer 230includes a semiconductor material and/or a dielectric material thatachieves desired etching selectivity, such as silicon, amorphoussilicon, semiconductor oxide, semiconductor nitride, semiconductoroxynitride, or semiconductor carbide. For example, in implementationswhere upper patterning layer 226 includes SiO₂, mandrel layer 230includes SiN. In some implementations, patterning layer 220 may beomitted, such that mandrel layer 230 includes a material that isdifferent than substrate 210 to achieve etching selectivity during anetching process, such that mandrel layer 230 can be removed using acorresponding etchant without significant etching of substrate 210, andvice versa. In such implementations, mandrel layer 230 can serve as anetching mask for patterning substrate 210.

A combination of deposition, lithography and/or etching processes areperformed to form mandrel layer 230, such that mandrels 232 extend fromupper patterning layer 226 as illustrated in FIG. 2A. For example,forming mandrel layer 230 includes depositing a masking layer (such asan amorphous silicon layer) over upper patterning layer 226, performinga lithography process to form a patterned resist layer over the maskinglayer, and performing an etching process to transfer a pattern definedin the patterned resist layer to the masking layer. The depositionprocess can include chemical vapor deposition (CVD), physical vapordeposition (PVD), atomic layer deposition (ALD), high density plasma CVD(HDPCVD), metal organic CVD (MOCVD), remote plasma CVD (RPCVD), plasmaenhanced CVD (PECVD), low-pressure CVD (LPCVD), atomic layer CVD(ALCVD), atmospheric pressure CVD (APCVD), spin coating, plating, otherdeposition methods, or combinations thereof. The lithography process caninclude forming a resist layer on the masking layer (for example, byspin coating), performing a pre-exposure baking process, performing anexposure process using a mask, performing a post-exposure bakingprocess, and performing a developing process. During the exposureprocess, the resist layer is exposed to radiation energy (such asultraviolet (UV) light, deep UV (DUV) light, or extreme UV (EUV) light),where the mask blocks, transmits, and/or reflects radiation to theresist layer depending on a mask pattern of the mask and/or mask type(for example, binary mask, phase shift mask, or EUV mask), such that animage is projected onto the resist layer that corresponds with the maskpattern. Since the resist layer is sensitive to radiation energy,exposed portions of the resist layer chemically change, and exposed (ornon-exposed) portions of the resist layer are dissolved during thedeveloping process depending on characteristics of the resist layer andcharacteristics of a developing solution used in the developing process.After development, the patterned resist layer includes a resist patternthat corresponds with the mask. Alternatively, the lithography processcan be implemented or replaced by other methods, such as masklesslithography, electron-beam writing, ion-beam writing, and/or nanoimprinttechnology. The etching process removes portions of the masking layer,where the etching process uses the patterned resist layer as an etchmask. The etching process can include a dry etching process, a wetetching process, other suitable etching process, or combinationsthereof. After the etching process, the patterned resist layer isremoved from the masking layer, for example, by a resist strippingprocess, leaving mandrel layer 230. In some implementations, mandrellayer 230 is formed by a double-patterning lithography (DPL) process,which is a method of constructing a pattern on a substrate by dividingthe pattern into two interleaved patterns. DPL allows enhanced ICfeature (for example, fin) density. Various DPL methodologies may beused including double exposure (such as using two mask sets), resistfreezing, EUV lithography, other suitable processes, or combinationsthereof.

In FIGS. 2B-2F, a fin cut first POPE process is performed to remove aportion of mandrel layer 230 (for example, a subset of mandrels 232),thereby defining active regions of FinFET device 200. In FIG. 2B, aguarding material layer 240 is formed over mandrel layer 230. In thedepicted embodiment, guarding material layer 240 is deposited overmandrel layer 230 by any suitable deposition process, such that guardingmaterial layer 240 fills spaces between mandrels 232. The depositionprocess can include CVD, PVD, ALD, HDPCVD, MOCVD, RPCVD, PECVD, LPCVD,ALCVD, APCVD, spin coating, plating, other deposition methods, orcombinations thereof. Guarding material layer 240 includes a materialthat is different than mandrel layer 230 to achieve etching selectivityduring an etching process, such that mandrel layer 230 can be removedusing a corresponding etchant without significant etching of guardingmaterial layer 240, and vice versa. In other words, guarding materiallayer 240 and mandrel layer 230 include materials having different etchrates. In some implementations, guarding material layer 240 can includea semiconductor material and/or a dielectric material that achievesdesired etching selectivity, such as silicon, amorphous silicon,semiconductor oxide, semiconductor nitride, semiconductor oxynitride, orsemiconductor carbide. For example, in some implementations wheremandrel layer 230 includes SiN, guarding material layer 240 includessilicon.

In FIG. 2C, a patterned resist layer 250 is formed over guardingmaterial layer 240. For example, a lithography process forms patternedresist layer 250. The lithography process can include forming a resistlayer on guarding material layer 240 (for example, by spin coating),performing a pre-exposure baking process, performing an exposure processusing a mask, performing a post-exposure baking process, and performinga developing process. During the exposure process, the resist layer isexposed to radiation energy (such as UV light, DUV light, or EUV light),where the mask blocks, transmits, and/or reflects radiation to theresist layer depending on a mask pattern of the mask and/or mask type,such that an image is projected onto the resist layer that correspondswith the mask pattern. Since the resist layer is sensitive to radiationenergy, exposed portions of the resist layer chemically change, andexposed (or non-exposed) portions of the resist layer are dissolvedduring the developing process depending on characteristics of the resistlayer and characteristics of a developing solution used in thedeveloping process. Alternatively, the lithography process can beimplemented or replaced by other methods, such as maskless lithography,e-beam writing, ion-beam writing, and/or nanoimprint technology. Afterdevelopment, patterned resist layer 250 includes a cut pattern thatcorresponds with the mask pattern, where the cut pattern exposes aportion of mandrel layer 230. For example, the cut pattern exposes asubset of mandrels 232, thereby defining protected mandrels 232A andunprotected (unwanted) mandrels 232B. Unprotected mandrels 232B are tobe removed during the fin cut first POPE process. In the depictedembodiment, the cut pattern defines an opening 252 aligned over(overlapping) unprotected mandrels 232B, where opening 252 partiallyexposes unprotected mandrels 232B. For example, unprotected mandrels232B include a top surface 260 defined between a sidewall 262 and asidewall 264, where patterned resist layer 250 masks sidewalls 262 andunmasks top surfaces 260 and sidewalls 264, thereby exposing guardingmaterial layer 240 covering top surfaces 260 and sidewalls 264.

In some implementations, patterned resist layer 250 partially masks topsurfaces 260 of unprotected mandrels 232B, partially exposing guardingmaterial layer 240 covering top surfaces 260. In some implementations,patterned resist layer 250 fully masks top surfaces 260 of unprotectedmandrels 232B, exposing only guarding material layer 240 coveringsidewalls 264. In some implementations, portions of unprotected mandrels232B on which guarding material layer 240 is to remain are protected bypatterned resist layer 250, while portions of unprotected mandrels 232Bfrom which guarding material layer 240 is to be removed are free ofpatterned resist layer 250. Further, though the depicted embodimentillustrates two unprotected mandrels 232B, the present disclosurecontemplates embodiments where the subset of mandrels 232 can includeany number of unprotected mandrels 232B. For example, the subset ofmandrels 232 exposed by the cut pattern can include a single unprotectedmandrel, where the cut pattern exposes a portion (such as at least onesidewall) of the single unprotected mandrel. In another example, thesubset of mandrels 232 exposed by the cut pattern can include more thantwo unprotected mandrels, where the cut pattern partially exposesunprotected mandrels near a perimeter of the cut pattern (for example,by exposing at least one sidewall) and fully exposes unprotectedmandrels disposed between unprotected mandrels near the perimeter (forexample, by exposing top surfaces and sidewalls defining unprotectedmandrels). The present disclosure further contemplates implementationswhere patterned resist layer 250 represents a patterned hard mask layer,which has been patterned with opening 252 as described herein. In suchimplementations, the patterned hard mask layer can include asemiconductor material and/or a dielectric material that achievesdesired etching selectivity (for example, between the patterned hardmask layer and guarding material layer 240), such as silicon,semiconductor oxide (for example, SiO₂), semiconductor nitride (forexample, SiN), semiconductor oxynitride (for example, SiOCN), orsemiconductor carbide (for example, SiCN).

In FIG. 2D, the cut pattern is transferred to guarding material layer240, thereby forming patterned guarding material layer 240 thatpartially exposes unprotected mandrels 232B. For example, the cutpattern defines an opening 270 that partially exposes unprotectedmandrels 232B. In some implementations, an etching process removesguarding material layer 240 exposed by opening 252 defined in patternedresist layer 250, such as guarding material layer 240 covering topsurfaces 260 and sidewalls 264 of unprotected mandrels 232B. Sincepatterned resist layer 250 masks sidewalls 262, guarding material layer240 remains on sidewalls 262. The etching process is a dry etchingprocess, a wet etching process, or combinations thereof. In the depictedembodiment, guarding material layer 240 is selectively etched fromportions of unprotected mandrels 232B without etching (or withoutsignificantly etching) unprotected mandrels 232B. Various etchingparameters can be tuned to selectively etch guarding material layer 240,such as etchant composition, etching temperature, etching solutionconcentration, etching time, etching pressure, source power, RF biasvoltage, RF bias power, etchant flow rate, other suitable etchingparameters, or combinations thereof. In some implementations, a wetetching process can selectively etch guarding material layer 240 using asuitable etching solution, such as a hydrofluoric acid (HF) basedsolution, a sulfuric acid (H₂SO₄) based solution, a hydrochloric (HCl)acid based solution, an ammonium hydroxide (NH₄OH) based solution, othersuitable etching solution, or combinations thereof. Thereafter,patterned resist layer 250 can be removed, for example, by a strippingprocess.

In FIG. 2E, unprotected mandrels 232B are removed from mandrel layer230. For example, an etching process is performed to remove unprotectedmandrels 232B exposed by opening 270 defined in guarding material layer240. Unprotected mandrels 232B are selectively etched without etching(or without significantly etching) guarding material layer 240 and/orpatterning layer 220 (in particular, upper patterning layer 226). Theetching process is a dry etching process, a wet etching process, orcombinations thereof. Various etching parameters can be tuned toselectively etch unprotected mandrels 232B, such as etchant composition,etching temperature, etching solution concentration, etching time,etching pressure, source power, RF bias voltage, RF bias power, etchantflow rate, other suitable etching parameters, or combinations thereof.In some implementations, a wet etching process can selectively etchunprotected mandrels 232B using a suitable etching solution, such as anHF based solution, an H₂SO₄ based solution, an HCl acid based solution,an NH₄OH based solution, other suitable etching solution, orcombinations thereof. Thereafter, in FIG. 2F, any remaining guardingmaterial layer 240 is removed, for example, by a selective etchingprocess as described above with reference to FIG. 2D, leaving protectedmandrels 232A disposed over patterning layer 220. Protected mandrels232A are separated by a space S1, such that mandrels 232A have a pitchP1 (for example, P1=w+S1) that is greater than P.

In FIGS. 2G-2I, a fin layer is defined in substrate 210 using mandrellayer 230, in particular, remaining protected mandrels 232B. In FIG. 2G,portions of patterning layer 220 are removed, for example, by an etchingprocess. For example, upper patterning layer 226, middle patterninglayer 224, and bottom patterning layer 222 are selectively etchedwithout etching (or without significantly etching) mandrel layer 230,such that protected mandrels 232A serve as an etching mask for removingthe portions of patterning layer 220. The etching process is a dryetching process, a wet etching process, or combinations thereof. Variousetching parameters can be tuned to selectively etch patterning layer220, such as etchant composition, etching temperature, etching solutionconcentration, etching time, etching pressure, source power, RF biasvoltage, RF bias power, etchant flow rate, other suitable etchingparameters, or combinations thereof. The present disclosure contemplatesany combination of etching processes and/or other processes for removingthe portions of patterning layer 220. Thereafter, in FIG. 2H, protectedmandrels 232 can be removed, for example, by an etching process. Theetching process can selectively etch protected mandrels 232A withoutetching (or without significantly etching) remaining portions ofpatterning layer 220, which provide patterning features 280 forpatterning substrate 210.

In FIG. 2I, portions of substrate 210 are removed to form a fin layer290, for example, by an etching process. Fin layer 290 includes an arrayof fins 292, where fins 292 have pitch P1 and adjacent fins 292 areseparated by space S1. A trench 294 is defined between fins 292 afterthe etching process. The etching process is a dry etching process, a wetetching process, or combinations thereof. In some implementations,substrate 210 is selectively etched without etching (or withoutsignificantly etching) patterning features 280, such that patterningfeatures 280 serve as an etching mask for removing the portions ofsubstrate 210. Various etching parameters can be tuned to selectivelyetch patterning layer 220, such as etchant composition, etchingtemperature, etching solution concentration, etching time, etchingpressure, source power, RF bias voltage, RF bias power, etchant flowrate, other suitable etching parameters, or combinations thereof. Insome implementations, various layers of patterning features 280 areremoved during the etching process. In some implementations, patterningfeatures 280 can be removed after forming fin layer 290.

FinFET device 200 may then undergo further processing to form variousfeatures and regions known in the art. For example, an isolationfeature(s) is formed in trench 294 to isolate fins 292, therebyisolation various active regions of FinFET device 200. The isolationfeature includes silicon oxide, silicon nitride, silicon oxynitride,other suitable isolation material, or combinations thereof. Theisolation feature can include different structures, such as STIstructures, deep trench isolation (DTI) structures, and/or localoxidation of silicon (LOCOS) structures. In some implementations, theisolation feature is formed by filling trench 294 with insulatormaterial (for example, by using a chemical vapor deposition process or aspin-on glass process). A chemical mechanical polishing (CMP) processmay be performed to remove excessive insulator material and/or planarizea top surface of the isolation feature. In some implementations, theisolation feature is formed by depositing an insulator material oversubstrate 210, such that the insulator material layer fills trench 294between fins 292, and etching back the insulator material layer. In someimplementations, the isolation feature includes a multi-layer structurethat fills trench 294, such as a silicon nitride layer disposed over athermal oxide liner layer. Subsequent processing may include one or moreion implantation processes (for example, into fins 292), may includeformation of one or more epitaxially-grown layers (which may includedoped layers), and may include formation of gate structures (such ashigh-K/metal gate stacks). In addition, subsequent processing mayinclude formation of sidewall spacers (for example, on the high-K/metalgate stacks), source/drain features (for example, epitaxially grownsource/drain features), etch stop layer(s), interlayer dielectric (ILD)layer(s), contact openings, contact metal, as well as variouscontacts/vias/lines and multilayers interconnect features (for example,metal layers and interlayer dielectrics) over substrate 210, configuredto connect the various features to form a functional circuit, which mayinclude one or more FinFET devices. In furtherance of the example, amultilayer interconnection may include vertical interconnects, such asvias or contacts, and horizontal interconnects, such as metal lines. Thevarious interconnection features may employ various conductive materialsincluding copper, tungsten, and/or silicide. In one example, a damasceneand/or dual damascene process is used to form a copper relatedmultilayer interconnection structure.

FIGS. 3A-3D illustrate fragmentary, diagrammatic top views of apatterned resist layer, such as patterned resist layer 250, disposedover a material layer, such as mandrel layer 230, according to variousaspects of the present disclosure. Though not depicted, guardingmaterial layer 240 is disposed between patterned resist layer 250 andmandrel layer 230, and guarding material layer 240 has been removed asexposed by an opening in patterned resist layer 250. In FIG. 3A, FinFETdevice 200 undergoes a conventional fin cut first process, whereunprotected mandrels 232B are fully exposed. For example, patternedresist layer 250 includes a cut pattern defined by an opening 270A thatfully exposes unprotected mandrels 232B, where an overlay window 295Aconstrains alignment of opening 270A with underlying mandrel layer 230.Overlay window 295A defines boundaries for cut edges 298 that defineopening 270A, ensuring that protected mandrels 232A remain covered byguarding material layer 240, while unprotected mandrels 232A arecompletely free of guarding material layer 240. These boundaries areconstrained by space S. For example, conventional fin cut first processoften specify an overlay (cut) budget of S/2, such that cut edges 298can shift no more than a distance S/2 from sidewalls of unprotectedmandrels 232B, in a direction that ensures that guarding material layer240 can be completely removed from unprotected mandrels 232B. As ICtechnologies continually progress towards smaller feature sizes (such as32 nanometers, 28 nanometers, 20 nanometers, and below), scaling down ofpitch P is shrinking space S between mandrels 232, drasticallydecreasing the overlay budget. This presents significant challenges tomanufacturing ever smaller IC features, such as fins of FinFET devices.One solution for increasing the overlay budget is to reduce width w ofmandrels 232, thereby increasing space S. However, this often results inhigh aspect ratio patterns, which require complicated etching processes.

By allowing partial exposure of unprotected mandrels 232B, overlaybudgets are significantly increased. For example, in FIG. 3B, FinFETdevice 200 undergoes a fin cut first POPE process as described herein,such that FIG. 3B provides a top view of FinFET device 200 thatcorresponds with FIG. 2D. In FIG. 3B, patterned resist layer 250includes a cut pattern defined respectively by an opening 270B, where anoverlay window 295B constrains alignment of opening 270B with underlyingmandrel layer 230. Overlay window 295B defines boundaries for cut edges298 defining opening 270B, ensuring that protected mandrels 232A arecovered by guarding material layer 240, while unprotected mandrels 232Aare partially free of guarding material layer 240. By allowing partialcoverage of unprotected mandrels 232B, boundaries can be constrained bypitch P. Accordingly, the fin cut first POPE process can increase theoverlay (cut) budget from S/2 (in other words, (P−w)/2) to P/2, suchthat cut edges 298 can shift a distance P/2, either direction, fromsidewalls of unprotected mandrels 232B, as depicted in FIG. 3B. Suchcompensates for larger overlay errors than conventional fin cut firstprocesses, allowing large shifts in opening 270B relative to mandrellayer 230. For example, in FIG. 3C, opening 270B is shifted to the left,fully exposing one unprotected mandrel 232B while partially exposinganother unprotected mandrel 232B. In FIG. 3D, opening 270B is shifted tothe right, fully exposing one unprotected mandrel 232B while partiallyexposing another unprotected mandrel 232B. In some implementations, thefin cut first POE processes can provide a 40% to 50% increase in overlay(cut) margins. And such is achieved without high aspect ratio patternsand/or without defects (such as residue portions of unprotected mandrels232B), increasing manufacturing ease and IC design flexibility.Different embodiments may have different advantages, and no particularadvantage is necessarily required of any embodiment.

FIGS. 4A-4I are fragmentary diagrammatic views of a FinFET device 300,in portion or entirety, at various fabrication stages (such as thoseassociated with method 100) according to various aspects of the presentdisclosure. FinFET device 300 may be included in a microprocessor, amemory, and/or other integrated circuit device. In some implementations,FinFET device 300 may be a portion of IC chip, an SoC, or portionthereof, that includes various passive and active microelectronicdevices such as resistors, capacitors, inductors, diodes, MOSFETs,CMOSs, BJTs, LDMOS transistors, high voltage transistors, high frequencytransistors, other suitable components, or combinations thereof. FinFETdevice 300 is similar in many respects to FinFET device 200.Accordingly, similar features in FIGS. 2A-2I and FIGS. 4A-4I areidentified by the same reference numerals for clarity and simplicity.FIGS. 4A-4I have been simplified for the sake of clarity to betterunderstand the inventive concepts of the present disclosure. Additionalfeatures can be added in FinFET device 300, and some of the featuresdescribed below can be replaced, modified, or eliminated in otherembodiments of FinFET device 300.

In FIG. 4A, similar to FinFET device 200, FinFET device 300 includessubstrate 210, patterning layer 220 disposed over substrate 210, andmandrel layer 230 disposed over patterning layer 220. Mandrel layer 230includes mandrels 232 (each having width w) having pitch P, whereadjacent mandrels 232 are separated by space S. Similar to fabricationof FinFET device 200 described with reference to FIGS. 2B-2F, in FIGS.4B-4F, a fin cut first POPE process is performed to remove a portion ofmandrel layer 230 (for example, a subset of mandrels 232), therebydefining active regions of FinFET device 300. The fin cut first POPEprocess achieves one or more of the advantages described herein withreference to fin cut POPE processes, including increasing overlay (cut)budgets.

In FIG. 4B, a guarding material layer 340 is formed over mandrel layer230. In contrast to guarding material layer 240 deposited over mandrellayer 230 of FinFET device 200 in FIG. 2B, guarding material layer 340does not fill spaces between mandrels 232. For example, guardingmaterial layer 340 is conformally deposited over mandrel layer 230 byany suitable deposition process, such that guarding material layer 340has a substantially uniform thickness over exposed surfaces of mandrellayer 230 and/or substrate 210. The deposition process can include CVD,PVD, ALD, HDPCVD, MOCVD, RPCVD, PECVD, LPCVD, ALCVD, APCVD, spincoating, plating, other deposition methods, or combinations thereof.Guarding material layer 340 includes a material that is different thanmandrel layer 230 to achieve etching selectivity during an etchingprocess, such that mandrel layer 230 can be removed using acorresponding etchant without significant etching of guarding materiallayer 340, and vice versa. In other words, guarding material layer 340and mandrel layer 230 include materials having different etch rates. Insome implementations, guarding material layer 340 includes asemiconductor material and/or a dielectric material that achievesdesired etching selectivity, such as silicon, amorphous silicon,semiconductor oxide, semiconductor nitride, semiconductor oxynitride, orsemiconductor carbide. For example, in some implementations wheremandrel layer 230 includes SiN, guarding material layer 340 includessilicon.

In FIG. 4C, a patterned resist layer 350 is formed over guardingmaterial layer 340. A lithography process may be performed to formpatterned resist layer 350, similar to the lithography process describedabove with reference to patterned resist layer 250. However, in contrastto patterned resist layer 250 formed over guarding material layer 240 ofFinFET device 200 in FIG. 2C, patterned resist layer 350 and guardingmaterial layer 340 combine to fill spaces between mandrels 232. Afterdevelopment, patterned resist layer 350 includes a cut pattern thatcorresponds with the mask pattern, where the cut pattern exposes aportion of mandrel layer 230. For example, the cut pattern exposes asubset of mandrels 232, thereby defining protected mandrels 232A andunprotected mandrels 232B. In FIG. 4C, the cut pattern includes anopening 352 aligned over (overlapping) unprotected mandrels 232B, whereopening 352 partially exposes unprotected mandrels 232B. Similar topatterned resist layer 250 formed over guarding material layer 240 ofFinFET device 200 in FIG. 2C, patterned resist layer 350 masks sidewalls262 and unmasks sidewalls 264 and top surfaces 260, thereby exposingguarding material layer 540 covering sidewalls 264 and top surfaces 260.In some implementations, patterned resist layer 350 partially masks topsurfaces 260 of unprotected mandrels 232B, partially exposing guardingmaterial layer 340 covering top surfaces 260. In some implementations,patterned resist layer 350 fully masks top surfaces 260 of unprotectedmandrels 232B, exposing only guarding material layer 340 coveringsidewalls 264. In some implementations, portions of unprotected mandrels232B on which guarding material layer 340 is to remain are protected bypatterned resist layer 350, while portions of unprotected mandrels 232Bfrom which guarding material layer 340 is to be removed are free ofpatterned resist layer 350.

In FIG. 4D, the cut pattern is transferred to guarding material layer340, thereby forming patterned guarding material layer 340 thatpartially exposes unprotected mandrels 232B. For example, the cutpattern defines an opening 370 that partially exposes unprotectedmandrels 232B. In some implementations, an etching process removesguarding material layer 340 exposed by opening 352 defined in patternedresist layer 350, such as guarding material layer 340 covering topsurfaces 260 and sidewalls 264 of unprotected mandrels 232B. Sincepatterned resist layer 350 masks sidewalls 262, guarding material layer340 remains on sidewalls 262. In the depicted embodiment, guardingmaterial layer 340 is selectively etched from portions of unprotectedmandrels 232B without etching (or without significantly etching)unprotected mandrels 232B. The etching process is similar to the etchingprocess used for removing guarding material layer 240, as described withreference to FIG. 2D.

In FIG. 4E, unprotected mandrels 232B are removed from mandrel layer230. For example, an etching process is performed to remove unprotectedmandrels 232B exposed by opening 370 defined in guarding material layer340. Unprotected mandrels 232B are selectively etched without etching(or significantly etching) guarding material layer 340 and/or patterninglayer 220 (in particular, upper patterning layer 226). The etchingprocess is similar to the etching process used for removing unprotectedmandrels 232B from FinFET device 200, as described above with referenceto FIG. 2E. Thereafter, in FIG. 4F, any remaining guarding materiallayer 340 is removed, for example, by a selective etching process, suchas described above with reference to FIG. 4D, leaving protected mandrels232A disposed over patterning layer 220. Protected mandrels 232A havepitch P1, where adjacent protected mandrels 232A are separated by S1. InFIGS. 4G-4I, FinFET device 300 undergoes further processing, similar toprocessing described above for FinFET device 200 with reference to FIGS.2G-2I. For example, fin layer 290 is defined in substrate 210 usingmandrel layer 230 (in particular, remaining protected mandrels 232B),where fin layer 290 includes fins 292. Similar to FinFET device 200,FinFET device 300 can undergo further processing, such as forming anisolation feature in trench 294 defined between fins 292 and/or formingother features of FinFET device 300.

FIGS. 5A-5F are fragmentary diagrammatic views of a FinFET device 400,in portion or entirety, at various fabrication stages (such as thoseassociated with method 100) according to various aspects of the presentdisclosure. FinFET device 400 can be included in a microprocessor, amemory, and/or other integrated circuit device. In some implementations,FinFET device 400 may be a portion of IC chip, an SoC, or portionthereof, that includes various passive and active microelectronicdevices such as resistors, capacitors, inductors, diodes, MOSFETs,CMOSs, BJTs, LDMOS transistors, high voltage transistors, high frequencytransistors, other suitable components, or combinations thereof. FIGS.5A-5F have been simplified for the sake of clarity to better understandthe inventive concepts of the present disclosure. Additional featurescan be added in FinFET device 400, and some of the features describedbelow can be replaced, modified, or eliminated in other embodiments ofFinFET device 400.

In FIG. 5A, FinFET device 400 includes a substrate (wafer) 410. In thedepicted embodiment, substrate 410 includes silicon. Alternatively oradditionally, substrate 410 includes another elementary semiconductor,such as germanium; a compound semiconductor, such as silicon carbide,gallium arsenide, gallium phosphide, indium phosphide, indium arsenide,and/or indium antimonide; an alloy semiconductor, such as silicongermanium (SiGe), GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP;or combinations thereof. Alternatively, substrate 410 is asemiconductor-on-insulator substrate, such as a silicon-on-insulator(SOI) substrate, a silicon germanium-on-insulator (SGOI) substrate, or agermanium-on-insulator (GOI) substrate. Semiconductor-on-insulatorsubstrates can be fabricated using separation by implantation of oxygen(SIMOX), wafer bonding, and/or other suitable methods.

Substrate 410 can include various doped regions (not shown) depending ondesign requirements of FinFET device 400. In some implementations,substrate 410 includes p-type doped regions (for example, p-type wells)doped with p-type dopants, such as boron (for example, BF₂), indium,other p-type dopant, or combinations thereof. In some implementations,substrate 410 includes n-type doped regions (for example, n-type wells)doped with n-type dopants, such as phosphorus, arsenic, other n-typedopant, or combinations thereof. In some implementations, substrate 410includes doped regions formed with a combination of p-type dopants andn-type dopants. The various doped regions can be formed directly onand/or in substrate 410, for example, providing a p-well structure, ann-well structure, a dual-well structure, a raised structure, orcombinations thereof. Doping may be implemented using a process such asion implantation or diffusion in various steps and techniques.

A fin layer 430 is defined over substrate 410. In the depictedembodiment, fin layer 430 includes an array of fins 432 (each having awidth w) extending from substrate 410, where adjacent fins 432 areseparated by a space S. Fins 432 have a pitch P, where pitch generallyrefers to a sum of a width of an IC feature (such as w of fins 432) anda width of a space adjacent to the IC feature (such as S between fins432) (in other words, P=w+S). Fins 432 are also referred to as finfeatures. In some implementations, pitch P is a minimum pitch achievablebetween fins 432 by a lithography process for a given technology node.In the depicted embodiment, fin layer 430 is a portion of substrate 410.In some implementations, fin layer 430 is formed in a material layer,such as a semiconductor material layer, of substrate 410. For example,in implementations where substrate 410 includes silicon, fin layer 430includes silicon. Alternatively, in some implementations, fin layer 430is defined in a material layer, such as a semiconductor material layer,overlying substrate 410.

A combination of deposition, lithography and/or etching processes areperformed to define fin layer 430 in substrate 410, such that fins 432extend from substrate 410 as illustrated in FIG. 5A. For example,forming fin layer 430 includes performing a lithography process to forma patterned resist layer over substrate 410 (or a material layerdisposed over substrate 410) and performing an etching process totransfer a pattern defined in the patterned resist layer to substrate410 (or the material layer disposed over substrate 410). The lithographyprocess can include forming a resist layer on substrate 410 (forexample, by spin coating), performing a pre-exposure baking process,performing an exposure process using a mask, performing a post-exposurebaking process, and performing a developing process. During the exposureprocess, the resist layer is exposed to radiation energy (such as UVlight, DUV light, or EUV light), where the mask blocks, transmits,and/or reflects radiation to the resist layer depending on a maskpattern of the mask and/or mask type (for example, binary mask, phaseshift mask, or EUV mask), such that an image is projected onto theresist layer that corresponds with the mask pattern. Since the resistlayer is sensitive to radiation energy, exposed portions of the resistlayer chemically change, and exposed (or non-exposed) portions of theresist layer are dissolved during the developing process depending oncharacteristics of the resist layer and characteristics of a developingsolution used in the developing process. After development, thepatterned resist layer includes a resist pattern that corresponds withthe mask. Alternatively, the lithography process can be implemented orreplaced by other methods, such as maskless lithography, electron-beamwriting, ion-beam writing, and/or nanoimprint technology. The etchingprocess removes portions of substrate 410, where the etching processuses the patterned resist layer as an etch mask. The etching process caninclude a dry etching process, a wet etching process, other suitableetching process, or combinations thereof. After the etching process, thepatterned resist layer is removed from substrate 410, for example, by aresist stripping process. In some implementations, fin layer 430 isformed by a DPL process, which is a method of constructing a pattern ona substrate by dividing the pattern into two interleaved patterns. DPLallows enhanced IC feature (for example, fin) density. Various DPLmethodologies may be used including double exposure (such as using twomask sets), resist freezing, EUV lithography, other suitable processes,or combinations thereof.

In FIGS. 5B-5F, a fin cut last POPE process is performed to remove aportion of fin layer 430 (for example, a subset of fins 432), therebydefining active regions of FinFET device 400. In FIG. 5B, a guardingmaterial layer 440 is formed over fin layer 430. In the depictedembodiment, guarding material layer 440 is deposited over fin layer 430by any suitable deposition process, such that guarding material layer440 fills spaces between fins 432. The deposition process can includeCVD, PVD, ALD, HDPCVD, MOCVD, RPCVD, PECVD, LPCVD, ALCVD, APCVD, spincoating, plating, other deposition methods, or combinations thereof.Guarding material layer 440 includes a material that is different thanfin layer 430 to achieve etching selectivity during an etching process,such that fin layer 430 can be removed using a corresponding etchantwithout significant etching of guarding material layer 440, and viceversa. In other words, guarding material layer 440 and fin layer 430include materials having different etch rates. In some implementations,guarding material layer 440 can include a semiconductor material and/ora dielectric material that achieves desired etching selectivity, such assilicon, amorphous silicon, semiconductor oxide, semiconductor nitride,semiconductor oxynitride, or semiconductor carbide. For example, inimplementations where fin layer 430 includes silicon, guarding materiallayer 440 can include SiO₂.

In FIG. 5C, a patterned resist layer 450 is formed over guardingmaterial layer 440. For example, a lithography process is performed toform patterned resist layer 450. The lithography process can includeforming a resist layer on guarding material layer 440 (for example, byspin coating), performing a pre-exposure baking process, performing anexposure process using a mask, performing a post-exposure bakingprocess, and performing a developing process. During the exposureprocess, the resist layer is exposed to radiation energy, where the maskblocks, transmits, and/or reflects radiation to the resist layerdepending on a mask pattern of the mask and/or mask type, such that animage is projected onto the resist layer that corresponds with the maskpattern. Since the resist layer is sensitive to radiation energy,exposed portions of the resist layer chemically change, and exposed (ornon-exposed) portions of the resist layer are dissolved during thedeveloping process depending on characteristics of the resist layer andcharacteristics of a developing solution used in the developing process.Alternatively, the lithography process can be implemented or replaced byother methods, such as maskless lithography, e-beam writing, ion-beamwriting, and/or nanoimprint technology. After development, patternedresist layer 450 includes a cut pattern that corresponds with the maskpattern, where the cut pattern exposes a portion of fin layer 430. Forexample, the cut pattern exposes a subset of fins 432, thereby definingprotected fins 432A and unprotected (unwanted) fins 432B. Unprotectedfins 432B are to be removed by the fin cut last process. In the depictedembodiment, the cut pattern includes an opening 452 aligned over(overlapping) unprotected fins 432B, where opening 452 partially exposesunprotected fins 432B. For example, unprotected fins 432B include a topsurface 460 defined between a sidewall 462 and a sidewall 464, wherepatterned resist layer 450 masks sidewalls 462 and unmasks sidewalls464, thereby exposing guarding material layer 440 covering sidewalls464. In furtherance of the depicted embodiment, patterned resist layer450 partially masks top surfaces 460 of unprotected fins 432B, partiallyexposing guarding material layer 440 covering top surfaces 460.

In some implementations, patterned resist layer 450 fully masks topsurfaces 460 of unprotected fins 432B, exposing only guarding materiallayer 440 covering sidewalls 464. In some implementations, portions ofunprotected fins 432B on which guarding material layer 440 is to remainare protected by patterned resist layer 450, while portions ofunprotected fins 432B from which guarding material layer 440 is to beremoved are free of patterned resist layer 450. Further, though thedepicted embodiment illustrates two unprotected fins, the presentdisclosure contemplates embodiments where the subset of fins 432 caninclude any number of unprotected fins. For example, the subset of fins432 exposed by the cut pattern can include a single unprotected fin,where the cut pattern exposes a portion (for example, a sidewall) of thesingle unprotected fin. In another example, the subset of fins 432exposed by the cut pattern can include more than two unprotected fins,where the cut pattern partially exposes unprotected fins 432B near aperimeter of the cut pattern (for example, by exposing at least onesidewall) and fully exposes unprotected fins 432B disposed betweenunprotected fins 432B near the perimeter (for example, by exposing topsurfaces and sidewalls defining unprotected fins 432B).

In FIG. 5D, the cut pattern is transferred to guarding material layer440, thereby forming an opening 470 in guarding material layer 440 thatexposes portions of unprotected fins 432B. For example, an etchingprocess removes guarding material layer 440 exposed by opening 452defined in patterned resist layer 450, such as guarding material layer440 covering sidewalls 464 of unprotected fins 432B and a portion ofguarding material layer 440 covering top surfaces 460 of unprotectedfins 432B. Since patterned resist layer 450 masks sidewalls 462 and aportion of top surfaces 460, guarding material layer 440 remains onsidewalls 462 and a portion of top surfaces 460. Guarding material layer440 is selectively etched from portions of unprotected fins 432B withoutetching (or significantly etching) unprotected fins 432B. The etchingprocess is a dry etching process, a wet etching process, or combinationsthereof. Various etching parameters can be tuned to selectively etchguarding material layer 440, such as etchant composition, etchingtemperature, etching solution concentration, etching time, etchingpressure, source power, RF bias voltage, RF bias power, etchant flowrate, other suitable etching parameters, or combinations thereof. Insome implementations, a wet etching process can selectively etchguarding material layer 440 using a suitable etching solution, such asan HF based solution, an H₂SO₄ based solution, an HCl acid basedsolution, an NH₄OH based solution, other suitable etching solution, orcombinations thereof. In the depicted embodiment, guarding materiallayer 440 is not completely removed from sidewalls 464. However, thepresent disclosure contemplates embodiments where the etching processcompletely removes guarding material layer 440 from sidewalls 464.Thereafter, patterned resist layer 450 can be removed, for example, by astripping process.

In FIG. 5E, unprotected fins 432B are removed from fin layer 430. Forexample, an etching process is performed to remove unprotected fins 432Bexposed by opening 470 defined in guarding material layer 440.Unprotected fins 432B are selectively etched without etching (orsignificantly etching) guarding material layer 440. The etching processis a dry etching process, a wet etching process, or combinationsthereof. Various etching parameters can be tuned to selectively etchunprotected fins 432B, such as etchant composition, etching temperature,etching solution concentration, etching time, etching pressure, sourcepower, RF bias voltage, RF bias power, etchant flow rate, other suitableetching parameters, or combinations thereof. In some implementations, awet etching process can selectively etch unprotected fins 432B using asuitable etching solution, such as an HF based solution, an H₂SO₄ basedsolution, an HCl acid based solution, an NH₄OH based solution, othersuitable etching solution, or combinations thereof. In the depictedembodiment, since guarding material layer 440 is not completely removedfrom sidewalls 464, a portion of unprotected fins 432B remains extendingfrom substrate 410. Such remaining portion can be referred to as residuefins. Thereafter, in FIG. 5F, any remaining guarding material layer 440is removed, for example, by a selective etching process as describedabove with reference to FIG. 5D, leaving protected fins 432A extendingfrom substrate 410. Protected fins 432A are separated by a space S1,such that protected fins 432A have a pitch P1 (for example, P1=w+S1)that is greater than P. A trench 294 is defined between protected fins432A.

FinFET device 400 may then undergo further processing to form variousfeatures and regions known in the art. For example, an isolationfeature(s) is formed in trench 480 to isolate protected fins 432A,thereby isolation various active regions of FinFET device 400. Theisolation feature includes silicon oxide, silicon nitride, siliconoxynitride, other suitable isolation material, or combinations thereof.The isolation feature can include different structures, such as STIstructures, deep trench isolation (DTI) structures, and/or localoxidation of silicon (LOCOS) structures. In some implementations, theisolation feature is formed by filling trench 480 with insulatormaterial (for example, by using a chemical vapor deposition process or aspin-on glass process). A chemical mechanical polishing (CMP) processmay be performed to remove excessive insulator material and/or planarizea top surface of the isolation feature. In some implementations, theisolation feature is formed by depositing an insulator material oversubstrate 410, such that the insulator material layer fills trench 480between protected fins 432A, and etching back the insulator materiallayer. In some implementations, the isolation feature includes amulti-layer structure that fills trench 480, such as a silicon nitridelayer disposed over a thermal oxide liner layer. Subsequent processingmay include one or more ion implantation processes (for example, intoprotected fins 432A), may include formation of one or moreepitaxially-grown layers (which may include doped layers), and mayinclude formation of gate structures (such as high-K/metal gate stacks).In addition, subsequent processing may include formation of sidewallspacers (for example, on the high-K/metal gate stacks), source/drainfeatures (for example, epitaxially grown source/drain features), etchstop layer(s), interlayer dielectric (ILD) layer(s), contact openings,contact metal, as well as various contacts/vias/lines and multilayersinterconnect features (for example, metal layers and interlayerdielectrics) over substrate 410, configured to connect the variousfeatures to form a functional circuit, which may include one or moreFinFET devices. In furtherance of the example, a multilayerinterconnection may include vertical interconnects, such as vias orcontacts, and horizontal interconnects, such as metal lines. The variousinterconnection features may employ various conductive materialsincluding copper, tungsten, and/or silicide. In one example, a damasceneand/or dual damascene process is used to form a copper relatedmultilayer interconnection structure.

The fin cut last POPE process described with reference to FIGS. 5A-5Fachieves advantages similar to the fin cut first POPE process, such asincreasing overlay (cut) budgets as described with reference to FIGS.3A-3D. For example, the fin cut last POPE process can increase theoverlay (cut) budget from S/2 (in other words, (P−w)/2) to P/2, allowinglarge shifts in opening 452 relative to mandrel layer 230. In someimplementations, the fin cut first POPE processes can provide a 40% to50% increase in overlay (cut) margins. Such can be achieved without highaspect ratio patterns and/or without defects (such as residue portionsof unprotected mandrels 232B that affect FinFET device characteristics),increasing manufacturing ease and IC design flexibility. For example,FIG. 6A provides various views of FinFET device 400 undergoing aconventional fin cut last process according to various aspects of thepresent disclosure, and FIG. 6B provides various views of FinFET device400 undergoing a fin cut last POPE process according to various aspectsof the present disclosure. FinFET device 400 is depictedthree-dimensionally before and after removal of unprotected fins 432B,where an X-CUT is a cross-sectional view of FinFET device 400 before andafter removal of unprotected fins 432B taken along an x-direction of oneof unprotected fins 432B and a Y-CUT is a cross-sectional view of FinFETdevice 400 before and after removal of unprotected fins 432B taken alonga y-direction.

In FIG. 6A, where FinFET device 400 undergoes conventional fin cut lastprocess, unprotected fins 432B are fully exposed. For example, apatterning layer 490 includes a cut pattern defined by an opening 492that fully exposes top surfaces of unprotected mandrels 432B.Unprotected fins 432B are then removed by an etching process, therebyforming trenches 494, where sidewalls of trenches 494 define line ends(such as ends of fins). In the X-CUT, trenches 494 include taperedsidewalls, which can result in fins not exhibiting desired criticaldimensions. In the Y-CUT, a portion of unprotected fins 432B remains intrenches 494 (referred to as residue fins), often arising from a highaspect ratio of trenches 494. Such defects can negatively affectperformance of FinFET device 400. To minimize issues arising fromtapered sidewalls and fin residue, conventional fin cut last processoften requires an anisotropic etching process.

In FIG. 6B, where FinFET device 400 undergoes fin cut last POPE process,unprotected fins 432B are partially exposed. For example, guardingmaterial layer 440 includes a cut pattern defined by opening 470 thatpartially exposes top surfaces and one of the sidewalls of unprotectedmandrels 432B, as described in detail above with reference to FIGS.5B-5F. Unprotected fins 432B are then removed by an etching process,thereby forming a trench 496, where sidewalls of trenches 496 defineline ends (such as ends of fins). In contrast to conventional fin cutprocess, fin cut last POPE process provides line end critical dimensioncontrol and/or reduces defects (such as fin residue). For example, incontrast to trenches 494, trench 496 includes non-tapered sidewalls,improving line end critical dimension. In another example, trench 496overcomes high aspect ratio limitations of conventional fin cut lastprocess, reducing the portion of unprotected fins 432B remaining intrench 496 after the etching process. Fin cut last POPE process thusprovides processing flexibility, allowing use of an isotropic etchingprocess for removing unprotected fins 432B, which can reduce etchingprocess requirements (such as time and energy). Different embodimentsmay have different advantages, and no particular advantage isnecessarily required of any embodiment.

FIGS. 7A-7F are fragmentary diagrammatic views of a FinFET device 500,in portion or entirety, at various fabrication stages (such as thoseassociated with method 100) according to various aspects of the presentdisclosure. FinFET device 500 may be included in a microprocessor, amemory, and/or other integrated circuit device. In some implementations,FinFET device 500 may be a portion of IC chip, an SoC, or portionthereof, that includes various passive and active microelectronicdevices such as resistors, capacitors, inductors, diodes, MOSFETs,CMOSs, BJTs, LDMOS transistors, high voltage transistors, high frequencytransistors, other suitable components, or combinations thereof. FinFETdevice 500 is similar in many respects to FinFET device 400.Accordingly, similar features in FIGS. 5A-5F and FIGS. 7A-7F areidentified by the same reference numerals for clarity and simplicity.FIGS. 7A-7F have been simplified for the sake of clarity to betterunderstand the inventive concepts of the present disclosure. Additionalfeatures can be added in FinFET device 500, and some of the featuresdescribed below can be replaced, modified, or eliminated in otherembodiments of FinFET device 500.

In FIG. 7A, similar to FinFET device 400, FinFET device 500 includessubstrate 410, where fin layer 430 is defined over substrate 410. In thedepicted embodiment, fin layer 430 includes an array of fins 432 (eachhaving a width w) extending from substrate 410, where fins 432 havepitch P and adjacent fins 432 are separated by space S. Similar tofabrication of FinFET device 400 described with reference to FIGS.5B-5F, in FIGS. 4B-4F, a fin cut last POPE process is performed toremove a portion of fin layer 430 (for example, a subset of fins 432),thereby defining active regions of FinFET device 500. The fin cut lastPOPE process achieves one or more of the advantages described hereinwith reference to fin cut POPE processes, including increasing overlay(cut) budgets.

In FIG. 7B, a guarding material layer 540 is formed over fin layer 430.In contrast to guarding material layer 540 deposited over fin layer 430of FinFET device 400 in FIG. 5B, guarding material layer 540 does notfill spaces between fins 432. For example, guarding material layer 540is conformally deposited over fin layer 430 by any suitable depositionprocess, such that guarding material layer 540 has a substantiallyuniform thickness over exposed surfaces of fin layer 430 and/orsubstrate 410. The deposition process can include CVD, PVD, ALD, HDPCVD,MOCVD, RPCVD, PECVD, LPCVD, ALCVD, APCVD, spin coating, plating, otherdeposition methods, or combinations thereof. Guarding material layer 540includes a material that is different than fin layer 430 to achieveetching selectivity during an etching process, such that fin layer 430can be removed using a corresponding etchant without significant etchingof guarding material layer 540, and vice versa. In other words, guardingmaterial layer 540 and fin layer 430 include materials having differentetch rates. In some implementations, guarding material layer 540includes a semiconductor material and/or a dielectric material thatachieves desired etching selectivity, such as silicon, amorphoussilicon, semiconductor oxide, semiconductor nitride, semiconductoroxynitride, or semiconductor carbide. For example, in implementationswhere fin layer 430 includes silicon, guarding material layer 540 caninclude SiO₂.

In FIG. 7C, a patterned resist layer 550 is formed over guardingmaterial layer 540. In some implementations, a lithography process isperformed to form patterned resist layer 550, similar to the lithographyprocess described above with reference to patterned resist layer 450.However, in contrast to patterned resist layer 450 formed over guardingmaterial layer 440 of FinFET device 400 in FIG. 5C, patterned resistlayer 550 and guarding material layer 540 combine to fill spaces betweenfins 432. After development, patterned resist layer 550 includes a cutpattern that corresponds with the mask pattern, where the cut patternexposes a portion of fin layer 430. For example, the cut pattern exposesa subset of fins 432, thereby defining protected fins 432A andunprotected fins 432B. In FIG. 7C, the cut pattern includes an opening552 aligned over (overlapping) unprotected fins 432B, where opening 552partially exposes unprotected fins 432B. Similar to patterned resistlayer 450 formed over guarding material layer 440 of FinFET device 400in FIG. 5C, patterned resist layer 550 masks sidewalls 462 and unmaskssidewalls 464, thereby exposing guarding material layer 540 coveringsidewalls 464. Patterned resist layer 550 also partially masks topsurfaces 460 of unprotected fins 432B, partially exposing guardingmaterial layer 540 covering top surfaces 460. In some implementations,patterned resist layer 550 fully masks top surfaces 460 of unprotectedfins 432B, exposing only guarding material layer 540 covering sidewalls464. In some implementations, portions of unprotected fins 432B on whichguarding material layer 540 is to remain are protected by patternedresist layer 550, while portions of unprotected fins 432B from whichguarding material layer 540 is to be removed are free of patternedresist layer 550.

In FIG. 7D, the cut pattern is transferred to guarding material layer540, thereby forming an opening 570 in guarding material layer 540 thatexposes portions of unprotected fins 432B. For example, an etchingprocess removes guarding material layer 540 exposed by opening 552defined in patterned resist layer 550, such as guarding material layer540 covering sidewalls 464 of unprotected fins 432B and a portion ofguarding material layer 540 covering top surfaces 460 of unprotectedfins 432B. Since patterned resist layer 550 masks sidewalls 462 and aportion of top surfaces 460, guarding material layer 540 remains onsidewalls 462 and a portion of top surfaces 460. Guarding material layer540 is selectively etched from portions of unprotected fins 432B withoutetching (or significantly etching) unprotected fins 432B. The etchingprocess is similar to the etching process used for removing guardingmaterial layer 440, as described with reference to FIG. 5D. However, inthe depicted embodiment, in contrast to removal of guarding materiallayer 440 from FinFET device 400 in FIG. 5D, guarding material layer 540is completely removed from sidewalls 464.

In FIG. 7E, unprotected fins 432B are removed from fin layer 430. Forexample, an etching process is performed to remove unprotected fins 432Bexposed by opening 570 defined in guarding material layer 540.Unprotected fins 432B are selectively etched without etching (orsignificantly etching) guarding material layer 540. The etching processis similar to the etching process used for removing unprotected fins432B from FinFET device 400, as described above with reference to FIG.5E. Thereafter, in FIG. 7F, any remaining guarding material layer 540 isremoved, for example, by a selective etching process as described abovewith reference to FIG. 7D, leaving protected fins 432A extending fromsubstrate 410 having a trench 485 defined therebetween. Similar toFinFET device 400, FinFET device 500 can undergo further processing,such as forming an isolation feature in trench 485 defined betweenprotected fins 432A and/or forming other features of FinFET device 500.

The present disclosure provides for many different embodiments of amethod for patterning integrated circuit devices, such as fin-like fieldeffect transistor devices. An exemplary method (which may be referred toas a POPE process) includes forming a material layer that includes anarray of fin features, and performing a fin cut process to remove asubset of the fin features. The fin cut process includes exposing thesubset of fin features using a cut pattern and removing the exposedsubset of the fin features. The cut pattern partially exposes at leastone fin feature of the subset of fin features. In implementations wherethe fin cut process is a fin cut first process, the material layer is amandrel layer and the fin features are mandrels. In suchimplementations, the method can further include, after performing thefin cut process, using the mandrel layer to pattern an underlying layer.In implementations where the fin cut process is a fin cut last process,the material layer is a substrate (or material layer thereof), and thefin features are fins defined in the substrate (or material layerthereof). In such implementations, the method can further includepatterning a substrate to form fins, wherein the material layer is thesubstrate, the fin features are the fins, and the fin cut process is afin cut last process. In some implementations, the at least one finfeature includes a first sidewall and a second sidewall, where the firstsidewall is exposed by the cut pattern and the second sidewall is notexposed by the cut pattern. In some implementations, the array of finfeatures have a pitch, and the fin cut process changes the pitch of thearray of fin features.

In some implementations, the exposing includes forming a guardingmaterial layer over the material layer, such that the guarding materiallayer covers the array of fin features. The exposing can further includeremoving the guarding material layer covering the subset of finfeatures, wherein the guarding material layer is partially removed fromthe at least one fin feature, such that the guarding material layerremains on a portion of the at least one fin feature. In someimplementations, the exposing further includes forming a patternedresist layer over the guarding material layer, where the patternedresist layer having an opening defined therein that partially overlapsthe at least one fin feature. The exposing can further include removinga portion of the guarding material layer exposed in the opening. In someimplementations, the material layer and the guarding material layerinclude materials that achieve etching selectivity during an etchingprocess used to remove the guarding material layer and an etchingprocess used to remove the exposed subset of the fin features. In someimplementations, the guarding material layer fills spaces between thefin features. In some implementations, the guarding material layerconformally covers the fin features.

Another exemplary method (which may be referred to as a POPE process)includes forming a plurality of mandrels over a substrate, forming aguarding material layer over the plurality of mandrels, removing aportion of the guarding material layer to partially expose a mandrel ofthe plurality of mandrels, and removing the partially exposed mandrel.Partially exposing the mandrel can include removing the guardingmaterial layer from a first sidewall of the mandrel, while the guardingmaterial layer remains on a second sidewall of the mandrel. In someimplementations, removing the portion of the guarding material layerincludes selectively etching the guarding material layer. In someimplementations, removing the portion of the guarding material layerfurther includes forming a patterned resist layer over the guardingmaterial layer, the patterned resist layer having an opening definedtherein that partially overlaps the mandrel, and further wherein theguarding material layer is selectively etched within the opening. Insome implementations, removing the partially exposed mandrel includesselectively etching the partially exposed mandrel.

Another exemplary method (which may be referred to as a POPE process)includes forming a plurality of fins over a substrate, forming aguarding material layer over the plurality of fins, removing a portionof the guarding material layer to partially expose a fin of theplurality of fins, and removing the partially exposed fin. Partiallyexposing the fin can include removing the guarding material layer from afirst sidewall of the fin, while the guarding material layer remains ona second sidewall of the fin. In some implementations, removing theportion of the guarding material layer includes selectively etching theguarding material layer. In some implementations, removing the portionof the guarding material layer further includes forming a patternedresist layer over the guarding material layer, the patterned resistlayer having an opening defined therein that partially overlaps the fin,and further wherein the guarding material layer is selectively etchedwithin the opening. In some implementations, removing the partiallyexposed fin includes selectively etching the partially exposed fin.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: forming a material layerthat includes an array of fin features; forming a guarding materiallayer directly on the material layer, wherein the guarding materiallayer covers the array of fin features; and performing a fin cut processon the material layer to remove a subset of the fin features, whereinthe fin cut process includes: exposing the subset of fin features andthe guarding material layer covering the subset of fin features based ona cut pattern defined in a patterned layer, wherein the cut patternpartially exposes at least one fin feature of the subset of finfeatures, removing the guarding material layer covering the subset offin features, wherein the guarding material layer is partially removedfrom the at least one fin feature, such that the guarding material layerremains on a portion of the at least one fin feature, removing theexposed subset of the fin features, and removing a remainder of theguarding material layer before performing any subsequent processing. 2.The method of claim 1, wherein the at least one fin feature includes afirst sidewall and a second sidewall, wherein the first sidewall isexposed by the cut pattern and the second sidewall is not exposed by thecut pattern.
 3. The method of claim 1, wherein the exposing furtherincludes: forming a patterned resist layer over the guarding materiallayer, the patterned resist layer having an opening defined therein thatpartially overlaps the at least one fin feature; and removing a portionof the guarding material layer exposed in the opening.
 4. The method ofclaim 1, wherein the material layer and the guarding material layerinclude materials that achieve etching selectivity during an etchingprocess used to remove the guarding material layer and an etchingprocess used to remove the exposed subset of the fin features.
 5. Themethod of claim 1, wherein the guarding material layer fills spacesbetween the fin features.
 6. The method of claim 1, wherein the guardingmaterial layer conformally covers the fin features.
 7. The method ofclaim 1, wherein the fin cut process is a fin cut first process, suchthat the material layer is a mandrel layer and the fin features aremandrels, and further wherein the method includes, after performing thefin cut process, using the mandrel layer to pattern an underlying layer.8. The method of claim 1, further including patterning a substrate toform fins, wherein the material layer is the substrate, the fin featuresare the fins, and the fin cut process is a fin cut last process.
 9. Themethod of claim 1, wherein the array of fin features have a pitch, andthe fin cut process changes the pitch of the array of fin features. 10.A method comprising: forming a plurality of mandrels over a substrate;forming a guarding material layer directly on the plurality of mandrels,wherein the guarding material layer covers the plurality of mandrels;removing a portion of the guarding material layer to partially expose amandrel of the plurality of mandrels; removing the partially exposedmandrel; and thereafter, patterning an underlying layer using theplurality of mandrels, wherein a remainder of the guarding materiallayer is entirely removed before the patterning.
 11. The method of claim10, wherein the partially exposing the mandrel includes removing theguarding material layer from a first sidewall of the mandrel, while theguarding material layer remains on a second sidewall of the mandrel. 12.The method of claim 10, wherein the removing the portion of the guardingmaterial layer includes selectively etching the guarding material layer.13. The method of claim 12, wherein the removing the portion of theguarding material layer further includes forming a patterned resistlayer over the guarding material layer, the patterned resist layerhaving an opening defined therein that partially overlaps the mandrel,and further wherein the guarding material layer is selectively etchedwithin the opening.
 14. The method of claim 10, wherein the removing thepartially exposed mandrel includes selectively etching the partiallyexposed mandrel.
 15. A method comprising: forming a plurality of finsover a substrate; forming a guarding material layer directly on theplurality of fins, wherein the guarding material layer covers theplurality of fins; removing a portion of the guarding material layer topartially expose a fin of the plurality of fins; removing the partiallyexposed fin; and after removing the partially exposed fin, removing aremainder of the guarding material layer to fully expose another fin ofthe plurality of fins.
 16. The method of claim 15, wherein the partiallyexposing the fin includes removing the guarding material layer from afirst sidewall of the fin, while the guarding material layer remains ona second sidewall of the fin.
 17. The method of claim 15, wherein theremoving the partially exposed fin includes selectively etching thepartially exposed fin.
 18. The method of claim 15, wherein the removingthe remainder of the guarding material layer includes removing all ofthe guarding material layer.
 19. The method of claim 15, wherein theremoving the portion of the guarding material layer includes selectivelyetching the guarding material layer.
 20. The method of claim 19, whereinthe removing the portion of the guarding material layer further includesforming a patterned resist layer over the guarding material layer, thepatterned resist layer having an opening defined therein that partiallyoverlaps the fin, and further wherein the guarding material layer isselectively etched within the opening.